Implantable devices have been implanted in, for example, airways to treat respiratory diseases. However, accumulation of mucus at the superior and inferior ends of an implantable device (e.g., a stent, an airway stent, etc.) has been a concern. Examples of stents include those disclosed in U.S. Pat. No. 4,655,771 (Wallsten), U.S. Pat. No. 5,662,713 (Andersen et al.), U.S. Pat. No. 5,876,448 (Thompson et al.), and U.S. Pat. Appl. Pub. No. 2012/0035715 (Robida et al.).
Proper mucus secretion is useful for clearing foreign matter from the respiratory system. Mucus may include a mixture of materials including, for example, water and glycoproteins and may be produced by, for example, serous cells, goblet cells, Clara cells, and type II alveolar cells in the bronchials and trachea. Stretching of the cells initiates signaling pathways from the CNS to secrete the mucus while the mechanical forces of the cilia and air flow work to transport the mucus through the airway to be expelled from the body.
Accumulation of mucus in an airway is not desirable. For example, accumulation of mucus may result in an infection or inflammation of tissue near the accumulation. Transport of mucus through an airway is dependent on a number of factors including, but not limited to, the composition and properties of the mucus, the quantity of accumulated mucus, the degree of adherence of the mucus to the walls of the airway, the dimensions and configuration of the airway (e.g., cross-sectional area), and the linear velocity of air flowing through the airway due to breathing, coughing, etc. For a given volumetric flow rate of air, the velocity will be higher at portions of the airway having a smaller cross-sectional area and lower at portions of the airway with a larger cross-sectional area. Airway stents have been designed to have a sufficient amount of radial force to maintain patency in the airway. Thus, reducing the cross sectional area in or near the stent ends (e.g., radial compression of the airway) to help prevent mucus buildup may be counterproductive with respect to the objective of maintaining patency.
Some patients that have respiratory diseases have been given a stent for palliative purposes. The presence of a rigid prosthesis may, in some circumstances, have a detrimental effect on the airway's ability to expel the mucus discussed below. As mucus moves through a stented airway, it has a tendency to accumulate at the ends of the stent. This may be due to a number of factors including the inability of the trachea/bronchi to compress enough to produce an airflow with sufficient force or velocity to move the mucus through the stented area because, e.g., the stent may prevent or inhibit radial compression or other constriction of the airway.
Some stents include a coating (e.g., a polymer coating) that can act as a barrier to tumor ingrowth. However, the choice of material and/or surface structure of the coating can influence, for example, the adherence of mucus to the coating.
Some attempts have been made to reduce accumulation of mucus in stents. For example, lubricious hydrophilic coatings of stent inner lumens have been formulated for the purpose of promoting mucus transport and to aid in the prevention of mucus buildup. (See, e.g., Merit™ Aero® fully covered tracheobronchial stent at http://endotek.merit.com/products/pulmonary.aspx (last visited Mar. 13, 2013).) However, in some circumstances, the use of hydrophilic materials has promoted mucus attachment, thereby increasing mucus accumulation, as well as the likelihood of airway plugging and infection.
Thus, there exists a desire for improved medical devices that reduce or eliminate one or more deficiencies of previous medical devices. For example, improved medical devices that reduce accumulation of mucus in a stented airway are desired. Improving one or more of the factors that facilitate movement of mucus through an airway may be useful to reduce or eliminate mucus accumulation. Improved medical devices that reduce or prevent mucus attachment and/or accumulation and thus reduce or eliminate the likelihood of an infection are desired.
The issue of mucous transport is one of many issues associated with placing an implant inside the body. Another issue associated with placing an implant inside the body is the patient's risk for infection, and or allergic reactions. Typically, given the nature of processing medical device components, the surface energy of such components is generally fairly high allowing most bodily fluids to wet on them. This can cause bacterial cultivation leading to infection.
It would be desirable to provide a medical device for implantation in the body that has been engineered to reduce the risk of infection and/or allergic reaction.
Yet another issue associated with placing an implant inside the body involves adhering the implant to the surrounding tissue. There is a need to provide implanted devices with features which will prevent the implant from migrating or at least reduce any possible migration.
Without limiting the scope of the present disclosure, a brief summary of some of the claimed embodiments of the present disclosure is provided below. Additional details of the summarized embodiments and/or additional embodiments of the present disclosure can be found in the detailed description.
A brief abstract of the technical disclosure in the specification is provided as well for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.
All US patents and applications, and all other published documents mentioned anywhere in this application, are incorporated herein by reference, each in its entirety.